What this ideal weight calculator does
The ideal weight calculator shows you four reference figures for your height: the three classic formulas — Devine, Robinson and Hamwi — and the healthy BMI range. None of them is "the answer" on its own. They were all developed for slightly different purposes, decades apart, with different assumptions. Seeing them side by side gives you a realistic range rather than a single misleading target.
The three formulas, written out
All three start with a base weight at 5 feet (152.4 cm) and add a fixed amount per inch above that.
- Hamwi (1964): Men 48 kg + 2.7 kg/inch over 5 ft · Women 45.5 kg + 2.2 kg/inch
- Devine (1974): Men 50 kg + 2.3 kg/inch over 5 ft · Women 45.5 kg + 2.3 kg/inch
- Robinson (1983): Men 52 kg + 1.9 kg/inch over 5 ft · Women 49 kg + 1.7 kg/inch
Hamwi was created at the Detroit Medical Center for diabetes dosing. Devine became the standard for medication dose calculations in clinical pharmacology. Robinson updated the figures for a more modern population. None were designed as personal goal-setting tools — that's a use case they ended up adopted for, somewhat awkwardly.
Why the BMI range often wins
A healthy weight isn't a single number; it's a band. For a 175 cm (5'9") person, the healthy BMI range (18.5-24.9) translates to about 57-76 kg. Sitting anywhere inside that range is fine for most adults. Insisting on, say, 70 kg exactly because a 1974 formula said so is more anxiety than science. The healthy BMI range also flexes with height in a way the formulas don't always capture cleanly.
Frame size and muscle mass
Two things the formulas ignore. Frame size: small-, medium- and large-framed people carry different amounts of bone and lean tissue at the same height. A rough wrist measurement (men >7.5 in / 19 cm = large; women >6.5 in / 16.5 cm = large) gives a quick frame check — large frames typically sit toward the higher end of the healthy range. Muscle mass: trained lifters often weigh well above the formula numbers with very healthy body composition. For both reasons, body fat percentage is a more honest measure of health than any weight figure.
Setting a realistic target
If you're heavier than the healthy range, don't aim for the bottom of it. Research consistently finds that losing 5-10% of starting weight gives most of the health benefits — improved blood pressure, blood sugar regulation and cardiovascular markers. Hit that, reassess, and decide whether to continue. The weight loss percentage calculator tracks that milestone explicitly.
Use with the other tools
The BMI calculator gives the standard BMI screen. The body fat calculator estimates body fat percentage — usually more informative than weight alone. The calorie calculator sets a daily calorie target for getting from where you are to where you'd like to be.